Servomotor vacuum seal

ABSTRACT

A servomotor having a front shell with an annular external surface which can vary from an ellipse to a circle joined to a concentric rear shell by a flange. The flange contacts the end plate of the rear shell and biases a peripheral bead of a diaphragm against a seat to seal the interior of the front and rear shells from the atmosphere.

U United States Patent [1 1 [111 3,768,379

Gardner 1 Oct. 30, 1973 SERVOMOTOR VACUUM SEAL 3,352,209 ll/l967 Cripc92/99 x {751' Inventor: Delbert J Gardner, South Bend, 3,656,4l3 4/1972Eggstcm 9. 92 99 x lnd.

Primary Examiner-Martin P. Schwadron l l Asslgneei The Bend Corporation,South Assistant Examiner-Abe Hershkovitz Bend Atz0rneyLe0 H. Mc Cormick,Jr. et a].

[22] Filed: Aug. 14, 1972 21 Appl. No.: 280,696 [57], ABSTRACT Aservomotor having a from shell with an annular ex- 52 us. Cl. 92/99temal Surface which can vary from an ellipse a 511 lm. Cl. FOlb 19/00,F16j 3/00 Cle joined COhCBhmC rear by flange h [58] Field 6: Search92/96, 98, 99 flange Contacts the end Plate of the Yeah and ases aperipheral bead of a diaphragm against a seat to [56] References Citedseal the interior of the front and rear shells from the UNITED STATESPATENTS atmosphere 3,188,920 6/1965 Hagar 92/99 X 7 Claims, 6 DrawingFigures SERVOMOTOR VACUUM SEAL- BACKGROUND OF THE INVENTION Theavailable space under the hood of recently manufactured automobiles hasbeen continually decreasing due to both the added accessories andrequired safety and pollution devices.

In automobiles equipped with one type of power brakes, a servomotor isrequired to provide an output force needed to operate the mastercylinder. These servomotors usually comprise a cylinder or shell havinga front section and a rear section joined together by a twist lock typeconnection similar to that shown in US. Pat. No. 3,109,346 with areciprocable piston located therein which supplies the output force.This type of twist lock arrangement extends past the periphery of theshell resulting in additional needed installation space. Attempts havebeen made to develop a connection between the front and rear shell bythe use of interlocking lugs which permit the diameter of the piston tobe only negligibly smaller than the shells. In such a servomotor, thediaphragm of the piston has an external marginal portion which isapproximately equal to the internal diameter of the front shell. Therear shell engages the marginal portion and presses the same against theinternal diameter. However, in manufacturing the shells, eccentricitydevelops and if the shells are notmatched, a vacuum leak can occur. Inattempting to compensate for these eccentricities, a greater spacebetween the lugs on the front shell and projections on the rear shellwas provided to allow a small amountof ra- SUMMARY OF THE'INVENTION Toreduce the overall'outside diameter of a servomotor for operating thepower brakes and judiciously utilizing the available'under the hoodspace of a vehicle, I have devised a means for joining anannular wallsection, whose surfacecan vary from an ellipse to a circle of a frontshell with an annular closure means to provide a vacuum seal. Theannular wall section has a closed end and an opened end. An inwardlyprojecting annular seat is secured adjacent the open end. A movable wallmeans located within the front shell is connected to a diaphragm meanswhich has an external bead with a concentric external surface a predetermined size larger than said annular wall section. The

bead has a slot on the inner face thereof which snaps over theperipheral edge of an end plate on the rear shell. The end plate withthe bead surrounding its pea means for joining a front shell with a rearshell to pro-' vide a vacuum seal for a servomotor.

It is another object of this invention to compensate foreccentricitybetween a front shell and a rear shell through a resilient bead ofadiaphragm having a diameter a predetermined size larger than theinterior of the front shell and a slot on the interior thereof whichsurrounds the peripheral edge of the rear shell which positions thediaphragm against the interior of the front 7 shell.

i It is still another object of this invention to provide means forproviding a vacuum seal between an annular front shell and a concentricrear shell.

These and other objects will be apparent fromreading this specificationand viewing the drawings.

BRIEF DESCRIPTION OF THE DRAWING bodiment of a closure means-similar tothat shown by FIG. 3.

FIG. 5 is an end view of a servomotor as shown in FIG. 1 with anelliptical external surface.

.FIG. 6 is a partial end view of aconical front shell having slots inthe peripheral surface thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The fluid pressureservomotor 10 shown in FIG. I has a front shell 12 with a closed end 14from which 'an annular wall section 16 extends rearwardly. The frontshell 12 is joined to a rear shell I8 through a closure means 20 to forma sealed cavity 22. The sealed cavity 22 is divided into a vacuumchamber 24 and a control chamber 26 by wall means 28 and diaphragm means30. The vacuum chamber 24 is connected to a source of vacuum usually bythe intake manifold of a vehicle. The diaphragm means 30 lliIS arollable section 32 with a bead 34 on the end thereof retained by saidclosure means 20 and an internal lip 36 which snaps into a groove 38 onhub means 40. The hub means 40 retains valve means 42 in'a manner fullydescribed in US. Pat. No. 3,106,873 and incorporated herein byreference. The valve means 42 is responsive to an input from push rod44' to interrupt the communication of vacuum from the front chamber 24through passage 46 to the rear chamber'26 and allow air under pressureto flow into the rear chamber 26 to create a pressure differential 7across the wall means 28 and diaphragm means 30.

This pressure differential creates a force which acts on the wall means28 causing the wall means 28 to move by overcoming return spring 48 andsupply an output force to push rod 50 which is connected to a mastercylinder (not shown) in a braking system. As the wall means 28 moves,rollable section 32 of the diaphragm means 30 rolls itself out or offthe forward surface 54 of the wall means 28 to continually change thevolum of the control chamber 26.

An annular seat 56, see FIG. 3, is formed by a groove I adjacent the endof the front shell 12 a predetermined distance from the opening 58. Thehead 34 of the diaphragm means 30 is located on the outside of the seat56. The bead 34 has an outside diameter concentric to the annular wallsection 16 and a slot 64 along the inner surface thereof. The rear shell18 has an end plate 62 with a peripheral edge 66 concentric to theannular wall section which extends into slot 64 and urges bead 34against the interior of the conical wall section 52 to form a radialvacuum seal. The outside surface 52 of the annular wall section is auniform surface throughout the entire length of the front chamber 24.Thus, the external surface of the servomotor willbe exemplified by theshape of the shell which can vary from a circle as shown in FIG. 2 tothat of an ellipse as shown in FIG. to meet space conditions. Theclosure means has a flange 60 which extends from the annular wallsection 52 at substantially a right angle to engage end plate 62 tocompress bead 34 against seat 56 as shown in FIG. 3 to form an axialvacuum seal.

By having the peripheral edge 66 bias the head 34 against the interiorof the annular wall section 16 and the flange 60 bias the bead 34against seat 56, a double seal is achieved. This double seal willcompensate for any eccentricity which may exist in the concentricity ofthe end plate an'dthe annular wall section and thereby a vacuum seal canpositively be achieved. The flange 60 completely covers the exterior ofbead 34 as shown in FIG. 2 to prevent any outside contaminant fromcontacting the diaphragm and causing deterioration thereof.

In the embodiments shown in FIGS. 4, 5 and 6 wherein elements areidentical to that shown in FIGS. 1,2 and 3 the same reference numeral isused.

In the embodiment shown in FIG. 4, the annular wall section 16 extendsin a uniform curve throughout the entire length of the servomotor 10. Anannular seat 70 is secured to the interior of the annular wall section16 a predetermined distance from the open end 58. The peripheral edge 66located in slot 64 will urge bead 34 against the annular wall section 16while flange 60 will cover the bead 34 and press the edge 72 againstannular seat 70 to achieve the double seal as recited above withreference to FIG. 1.

In some situations because of the thickness of the material from whichthe front shell 12 is constructed, it may be necessary to provide slots76, see FIG. 6, along radial lines 78 extending from an axial line ofthe opening 74 inthe front shell 12 to form tabs 79 and 80. The tabs 79are successively bent over into contact with the end plate 62 while tabs80 bias the bead 34 into contact with the annular seat 56 to develop theradial and axial vacuum seal for the front and rear chambers in theservomotor 10 as described above. The width of the slots 76 are suchthat in the position shown in FIG. 6, bead 34 is substantially coveredto prevent contamination in the atmosphere from contacting thediaphragm.

To further utilize the available space under a vehicles hood it may beoccasioned that a servomotor whose outside surface 16 of the servomotor10 follows a path of a point whose distance from two fixed points isconstant or approaches an ellipse similar to that shown in FIG. 5 can bepositioned where a servomotor whose outside surface is substantiallycircular to that in FIG. 2 will not fit. When an elliptically shapedservo motor is used, the annular wall section 16, the wall means 28,diaphragm means 30, and end plate 62 will have a common central axiswhich will permit the input push rod 44, hub means and output push rodto be in axial alignment as shown in FIG. 1. Thus, the same valve means42 can be utilized in both the circular and elliptical shapedservomotors.

I claim:

1. A servomotor for use in a power brakingsystem comprising:

a front shell having a closed end with a rearwardly extending annularwall section terminating with an open end, said closed end having anaxial opening therein;

an inwardly projecting annular seat secured to said annular wall sectiona predetermined distance from said open end;

wall means located in said front shell with an external surfaceconcentric to said annular wall section, said wall means being adaptedto move within said front shell toward said closed end;

diaphragm means secured to said wall means having a rollable portionlocated between the external surface and said annular wall section witha bead on the end thereof, said bead being concentric to said annularwall section, said bead having a slot on an interior surface thereof;

a rear shell having an end plate with a peripheral edge concentric tosaid annular wall section, said peripheral edge extending into said slotto position said bead against said annular wall section and form a firstchamber between the front shell and the diaphragm means and a secondchamber between the rear shell and the diaphragm means;

said first and second chambers being connected to a source of vacuum;

closure means extending from said annular wall section into contact withsaid end plate for biasing said bead into contact with said annular seatto seal the first and second chambers connected to vacuum from theatmosphere;

resilient means located in said first chamber for urging said diaphragmmeans against said end plate of the rear shell; and

control means responsive to an operator for inter rupting the vacuumcommunication to the second chamber and allowing air under pressure intothe I second chamber for creating a pressure differential across saiddiaphragm and wall means, said'pres-' s'uredifferential causing saidwall means to move and transmit an operational force to an output rodretained in said'axial opening.

2. The servomotor, as recited in cliam I, wherein said annular wallsection, said closed end, wall means, diaphragm means and end plate havea common central axis.

3. The servomotor, as recited in claim 2, wherein the edges of saidannular wall section, external surface of said wall means, head of saiddiaphragm and peripheral edge of said end plate each follow acorresponding concentric path of points respectively whose distance fromtwo fixed points is constant.

4. The servomotor, as recited in claim 3, wherein said closure meansincludes:

a series of tabs extending from the open end of said annular wallsection, said tabs covering said bead to protect the diaphragm fromdeterioration.

5. The servomotor, as recited in claim 3, wherein said closure meansincludes:

a continuous flange integral with said annular wall section, said flangecompletely covering said bead to protect the diaphragm means from.deterioedges of said annular wall section, external surface of 5 6 saidwall means, bead of said diaphragm and peripheral edge of said end platefollow corresponding concentric plan curves that approximate an ellipse.

1. A servomotor for use in a power braking system comprising: a front shell having a closed end with a rearwardly extending annular wall section terminating with an open end, said closed end having an axial opening therein; an inwardly projecting annular seat secured to said annular wall section a predetermined distance from said open end; wall means located in said front shell with an external surface concentric to said annular wall section, said wall means being adapted to move within said front shell toward said closed end; diaphragm means secured to said wall means having a rollable portion located between the external surface and said annular wall section with a bead on the end thereof, said bead being concentric to said annular wall section, said bead having a slot on an interior surface thereof; a rear shell having an end plate with a peripheral edge concentric to said annular wall section, said peripheral edge extending into said slot to position said bead against said annular wall section and form a first chambeR between the front shell and the diaphragm means and a second chamber between the rear shell and the diaphragm means; said first and second chambers being connected to a source of vacuum; closure means extending from said annular wall section into contact with said end plate for biasing said bead into contact with said annular seat to seal the first and second chambers connected to vacuum from the atmosphere; resilient means located in said first chamber for urging said diaphragm means against said end plate of the rear shell; and control means responsive to an operator for interrupting the vacuum communication to the second chamber and allowing air under pressure into the second chamber for creating a pressure differential across said diaphragm and wall means, said pressure differential causing said wall means to move and transmit an operational force to an output rod retained in said axial opening.
 2. The servomotor, as recited in cliam 1, wherein said annular wall section, said closed end, wall means, diaphragm means and end plate have a common central axis.
 3. The servomotor, as recited in claim 2, wherein the edges of said annular wall section, external surface of said wall means, bead of said diaphragm and peripheral edge of said end plate each follow a corresponding concentric path of points respectively whose distance from two fixed points is constant.
 4. The servomotor, as recited in claim 3, wherein said closure means includes: a series of tabs extending from the open end of said annular wall section, said tabs covering said bead to protect the diaphragm from deterioration.
 5. The servomotor, as recited in claim 3, wherein said closure means includes: a continuous flange integral with said annular wall section, said flange completely covering said bead to protect the diaphragm means from deterioration.
 6. The servomotor, as recited in claim 5, wherein said flange and annular seat compress said bead causing the bead to resiliently flow against said annular wall section and peripheral edge of the end plate to create a vacuum seal.
 7. The servomotor, as recited in claim 2, wherein the edges of said annular wall section, external surface of said wall means, bead of said diaphragm and peripheral edge of said end plate follow corresponding concentric plan curves that approximate an ellipse. 